Hi all,
One seemingly simple query that joins two tables takes a long time for me.
This is my library.
mysql> show table status from nber1999;
+-----------+--------+---------+------------+----------+----------------+-------------+------------------+--------------+-----------+----------------+---------------------+---------------------+------------+-------------------+----------+----------------+---------+
| Name | Engine | Version | Row_format | Rows | Avg_row_length
| Data_length | Max_data_length | Index_length | Data_free |
Auto_increment | Create_time | Update_time | Check_time
| Collation | Checksum | Create_options | Comment |
+-----------+--------+---------+------------+----------+----------------+-------------+------------------+--------------+-----------+----------------+---------------------+---------------------+------------+-------------------+----------+----------------+---------+
| compusta1 | MyISAM | 10 | Dynamic | 4906 | 77
| 379464 | 281474976710655 | 1024 | 0 |
NULL | 2009-08-27 23:56:47 | 2009-08-27 23:56:47 | NULL |
latin1_swedish_ci | NULL | | |
| pat1 | MyISAM | 10 | Dynamic | 2089903 | 96
| 201936072 | 281474976710655 | 1024 | 0 |
NULL | 2009-08-27 23:55:48 | 2009-08-27 23:55:56 | NULL |
latin1_swedish_ci | NULL | | |
+-----------+--------+---------+------------+----------+----------------+-------------+------------------+--------------+-----------+----------------+---------------------+---------------------+------------+-------------------+----------+----------------+---------+
5 rows in set (0.00 sec)
And the relevant rows in my slow query log file is:
/usr/sbin/mysqld, Version: 5.0.75-0ubuntu10.2-log ((Ubuntu)). started with:
Tcp port: 3306 Unix socket: /var/run/mysqld/mysqld.sock
Time Id Command Argument
# Time: 090828 10:36:17
# u...@host: root[root] @ localhost []
# Query_time: 478 Lock_time: 0 Rows_sent: 0 Rows_examined: 1251
use nber1999;
create table nber1999.pat select a.*, b.assname, b.cname, b.cusip,
b.own, b.pname, b.sname
from nber1999.pat1 as a inner join nber1999.compusta1 as b
on a.assignee=b.assignee;
My operating system is ubuntu 9.04. I set configuration variables as
follows:
[mysqld]
key_buffer = 1024M
table_cache = 256
query_cache_type = 1
query_cache_limit = 2M
query_cache_size = 20M
[isamchk]
key_buffer = 16M
Can anyone give me some hint on how to speed this query up? Thanks.
I tried to tune mysql by using a script from
http://mediakey.dk/~cc/optimize-mysql-performance-with-mysqltuner/
and got
>> MySQLTuner 1.0.0 - Major Hayden <ma...@mhtx.net>
>> Bug reports, feature requests, and downloads at http://mysqltuner.com/
>> Run with '--help' for additional options and output filtering
Please enter your MySQL administrative login: root
Please enter your MySQL administrative password:
-------- General Statistics
--------------------------------------------------
[--] Skipped version check for MySQLTuner script
[OK] Currently running supported MySQL version 5.0.75-0ubuntu10.2-log
[OK] Operating on 64-bit architecture
-------- Storage Engine Statistics
-------------------------------------------
[--] Status: +Archive -BDB -Federated -InnoDB -ISAM -NDBCluster
[--] Data in MyISAM tables: 584M (Tables: 6)
[OK] Total fragmented tables: 0
-------- Performance Metrics
-------------------------------------------------
[--] Up for: 30m 47s (131 q [0.071 qps], 42 conn, TX: 35K, RX: 7K)
[--] Reads / Writes: 100% / 0%
[--] Total buffers: 1.0G global + 2.6M per thread (100 max threads)
[OK] Maximum possible memory usage: 1.3G (34% of installed RAM)
[OK] Slow queries: 0% (1/131)
[OK] Highest usage of available connections: 2% (2/100)
[OK] Key buffer size / total MyISAM indexes: 1.0G/74.0K
[!!] Query cache efficiency: 0.0% (0 cached / 67 selects)
[OK] Query cache prunes per day: 0
[OK] Temporary tables created on disk: 19% (21 on disk / 107 total)
[OK] Thread cache hit rate: 95% (2 created / 42 connections)
[OK] Table cache hit rate: 75% (24 open / 32 opened)
[OK] Open file limit used: 4% (49/1K)
[OK] Table locks acquired immediately: 100% (41 immediate / 41 locks)
-------- Recommendations
-----------------------------------------------------
General recommendations:
MySQL started within last 24 hours - recommendations may be inaccurate
Variables to adjust:
query_cache_limit (> 2M, or use smaller result sets)
Best,
Jia
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